Process of refining cracked distillates



Patented July 17, 1934 PROCESS OF 'REFINING CRACKED DISTILLATES JacqueC. Morrell, Chicago, Ill., assignor to Universal Oil Products Company,Chicago, 111., a corporation of South Dakota No Drawing. ApplicationJune 19, 1931, Serial No. 545,481

5 Claims. (01. 196-40 alkali and alkaline earth metals, being extremelystable. While hydrobromic and hydriodlc acids are in general lessreactive than the two preceding, they react readily with certain typesof organic compounds, for example, the oleflns, and in this respect arespecially adaptable for use in the present invention.

The effects produced in the refining of petroleum distillate withsulphuric acid and halogen acids according to the process of the presentinvention, while generally similar, will also vary to a degree somewhatdependent upon the nature of the This invention relates to the treatmentof hydrocarbon oils, and refers particularly to the treatment of thelower boiling distillates from crude petroleums or from-the cracking ofthe heavier portions thereof.

More specifically the invention has reference to the treatment of suchdistillates by chemical reagents adapted to bring them to a degree ofrefinement demanded by commercial specifications for motor fuels, etc.

Refining of petroleum distillates, particularly cracked distillates, isnecessitated by the fact that they contain material amounts ofunsaturated hydrocarbons which tend to polymerize and deposit gums andalso by the fact that they contain larger percentages of sulphur thanare usually allowable. Of the various methods of treating for theremoval of the necessary amounts of these undesirable impurities the useof sulphuric acid is most common, treatment being conducted principallyon the oils in the liquid phase. It is with improvements in the methodsof refining these distillates that the present invention is concerned, aclear description of the process of the invention being given in thefollowing specification from which the aims and objects thereof willmore fully appear.

In one specific embodiment the invention comprises treating hydrocarbonoils simultaneously with sulphuric acid and a halogen acid. Sulphuricacid of varying concentration from a relatively dilute aqueous solutionup to and including acids containing free sulphur trioxide may be usedand any one of the halogen acids, which group includes hydrofluoricacid, hydrochloric acid, hydrobromic acid and hydriodic acid.

The properties of the halogen acids in general vary progressively in theorder given above. For example, the reactivity of the acids decreasesfrom hydrofluoric to hydriodic in practically all chemical reactions inwhich they are involved. Hydrofluoric acid, for example, as the mostactive member of the series, reacts with extreme vigor with metals toform fluorides, decomposes silicates with the production of metalfluorides and liberation of silicon as silicon tetra fluoride and ingeneral presents great difliculties in handling. Hydrochloric acid,while less reactive than hydrofluoric, still exhibits a high degree ofactivity, the chlorides of many metals, for example, of the halogen acidOFFICE as well as upon the strength and amount of sulphuric acidemployed and other conditions of treatment. It has been found thatefliciency of the treatment is increased so that smaller quantities ofthe reagents are needed with resultant economy in cost of treatment.

The halogen acids may be introduced into the sphere of reaction eitheras such from outside sources or may be generated in situ from halogencompounds with which the sulphuric acid interacts to liberate thehalogen acid. For example, an effective treatment may be conducted uponpetroleum oils by suspending finely divided fluorspar, or calciumfluoride in the oil to be treated and then adding the necessary amountsof sulphuric acid to produce the desired treating effects, the sulphuricacid reacting with the fluorspar to form sponding equivalent of calciumsulphate.

free hydrofluoric acid and a corre- Similarly, other metallic halides'may be used which liberate the brought into corresponding halogen acidwhen contact with sulphuric acid. For

example, to generate hydrochloric acid sodium chloride or common saltmay be employed and to generate hydrobromic or hydriodic acid sodiumbromide or s tively.

odium iodide may be used respec- The use of hydriodic acid has beenfound to possess special advantages in that there is a liberation offree iodine due to the oxidizing efiect of the sulphuric acid, theliberated iodine being particularly active in inducing polymerizationand catalyzing the treating reactions.

The process of the invention may be employed as a single treatment insome instances, but it is preferably used in conjunction with otherrefining treatments. As an example of a series of treatments which maybe used the following may be mentioned which has been found to producegood results in the treatment of cracked distillates:

1. Treatment with caustic soda to remove hydrogen sulphide;

2. Treatment with sulfuric acid and a halogen acid according to theprocess of the present invention;

3. Treatment with strong caustic soda;

4. Redistillation to produce an end point gasoline;

5. Treatment with dilute caustic and water wash.

While the process of the invention may be con-= ducted in many types andarrangements of equipment and is not limited to any particular type ofequipment, a few forms of apparatus may be mentioned, the most commonbeing the batch agitator generally employed in petroleum refineries. Insuch an agitator, which is essentially a vertical cylindrical tank witha cone bottom, the reagents may be added while the oil is beingcirculated by an outside pump irom the bottom of the cone back into thetop of the agitator, circulation being continued until the reagents arespent or until the desired treating efiect is obtained, such a treatmentbeing followed by a period for subsidence of reaction products which arethen drawn from the cone.

Another type of treating apparatus that may be employed is the so-calledcontinuous treating plant commonly comprising a series of mixersfollowed by settling drums with the necessary refining and washingagents added to the oil stream as it passes through the mixing devices.In still other cases reagents may be added to the stream of oil enteringa heating element in which case treatments may be efiected atsuperatmospheric temperatures and pressures, the treated products beingdischarged directly into a suitable fractionating column from whencerefined end point vapors are taken, condensed and collected.

Examples of results obtainable by treating cracked distillates withmixtures of sulphuric and halogen acids might be multipliedconsiderably,

but a few typical cases will be suficent to indi' cate the good resultsobtainable.

As one example of a treatment comprised within the scope of theinvention and results obtainable therefrom, the treatment of aCalifornia cracked distillate may be mentioned. Such a distillate asoriginally condensed from the cracking unit may have an end point of 500F. and yield upon subsequent distillation without chemical treatmentother than caustic soda solutions 75% of a 410 F. end point gasolinewhich has a color of only 15 on the Saybolt scale, a gum content by thecopper dish method of I00 rugs. and a sulphur content of 0.25%.According to one modification of the process of the invention the rawdistillate may be treated after washing with caustic soda to removehydrogen sulphide and minor amounts of mercaptans, with five pounds perbarrel of 66 B. sulphuric acid at normal temperatures, there beingsuspended in the 011 undergoing treatment finely divided fluorspar atthe rate of 1.5 pounds per barrel of distillate treated. After thistreatment followed by suitable neutralization and sweetening steps andredistilling for end point gasoline, the finished product may have thefollowing properties:

Gums by the copper dish method- 30 mgs. Sulphur 0.1% Color +30 SayboltColor after 4 hours exposure to sunlight 26 invention a pressuredistillate resulting from the f? cracking of a Mid-continent gas oil maybe treated in the liquid phase at ordinary temperatures with six poundsper barrel of 66 Be. sulphuric acid and one pound per barrel ofhydrochloric acid, the latter being injected as a substantiallyanhydrous gas during the sulphuric acid treatment which, is convenientlyconducted by cir culating the acid from the cone back into top of abatch agitator. The raw or untreated distillate may have a 480 F. endpoint and yield upon distillation approximately of a gasoline of 410 endpoint which, however, is unsuited for use as motor fuel due to itshaving a gum content of 400 rngs. by the copper dish method,

a color of i l on the Saybolt scale and a sulphur content of 0.5%.-Redistillation of the pressure distillate after treatment in the mannerdescribed followed by neutralizing and sweetening may result in adistinct improvement in the gasoline fraction as compared with thegasoline pro duced from the raw material, the properties 02 the treatedgasoline being as follows:

Gums 20 mgs. Color +30 Saybolt Color after 4 hours exposure to sunlight2d Sulphur 0 .15

Treatments on an experimental scale using hydrobromic or hydriodic acidin conjunction with sulphuric acid treatments also have shown effects ofa higher order than those obtainable by the use of sulphuric acid alone,but as the present cost of these reagents is prohibitive from acommercial standpoint their use is apparently not practical in theimmediate iuture and is merely mentioned to indicate that they may beused advantageously if economic conditions should result in a loweringof their cost.

The preceding specification and citations 05.

examples of results obtainable by the use of the present invention willindicate in a sufficiently clear manner that a process has beendisclosed which possesses manifest advantages. However, many otherapplications are possible than the ones specifically described and theyare not to be construed in a limiting sense upon the broad scope of theinvention.

I claim as myinvention:

1. A process of refining cracked hydrocarbon distillate, which comprisessubjecting the distil- 4. A process for refining cracked hydrocarbondistillate which comprises subjecting the distillate to the action ofsulphuric acid containing a halogen acid selected from the groupconsisting of hydrofluoric acid, hydrobromic acid and hydriodic acid.

5. A process for refining cracked hydrocarbon distillate which comprisessubjecting the distillate to the action of sulphuric acid containinghydrobromic acid.

JACQUE C. MORRELL.

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